A number of requirements exist for a pressure sensitive label including printed indicia thereon and adhered to a product that includes one or more materials therein that are capable of migrating through and staining a label adhered to such a product. In particular, and most particularly in connection with rubber based products such as vehicle tires, these requirements include good printability characteristics with flexographic inks and thermal transfer; good flexibility and drapability to permit desired conformability to the surface of the product; ease of dispensing and excellent stain resistance. It is this last requirement that has been the most difficult to achieve. It appears that migratory materials in a number of products, and in particular rubber-based products such as tires, tend to migrate into attached labels causing undesired surface staining of the label. Label-staining migratory materials also are present in a variety of other products, such as candles and batteries, and the labels of this invention are usable with any of these products. The exact nature of the migratory materials from rubber-based products such as tires is not known at this time but the staining problem created by such materials is quite prevalent during sustained periods of storage of the labeled products.
A number of film structures have been tested in connection with the stain resistance requirement. PVdC coated white films have worked fairly well in reducing staining; however they have presented environmental issues. Metallized films also have worked well, but for many applications, and in particular in applications on vehicular tires, the appearance of such metallized films is not desirable.
Stain resistant labels for use on tires are disclosed in Conwell et al. U.S. Publication 2004/0095244 and also in Majumdar U.S. Pat. No. 6,221,453. The labels disclosed in the Conwell '244 publication include a barrier layer or film of polyester, e.g., PET. The labels disclosed in the Majumdar '453 patent discloses a variety of materials that act as barriers to stain creating components in tires, including metals, polyesters, cellophane, fluorinated polymers, poly(vinyl acetate), poly(vinyl alcohol), poly(vinyl pyrrolidone) or its copolymer with vinyl acetate.
A number of the prior art components for use in preventing staining in tire labels, either need to be coextruded as part of the label construction or, due to a lack of elasticity, need to be applied as a separate coating after biaxial orientation of other, coextruded components of the label. Extrusion equipment may not be available to handle the coextrusion of a label product with an additional barrier layer. In addition, other prior art components are provided as a separate film and therefore can only be applied to the coextruded label structure off-line, after biaxial orientation of the coextruded components of the label.
Solvent resistant label structures attached to containers including a hydrocarbon solvent therein are disclosed in Wilkie U.S. Pat. No. 8,158,227, assigned to the assignee of this application, Taghleef Industries, Inc. (formerly Applied Extrusion Technologies, Inc.). The label disclosed in the '227 patent eliminates or minimizes the distortion of the label when the label is exposed to the solvent in, or on the surface of the container. The labels disclosed in the '227 patent do not relate to or address any staining issues of labels attached to products including migratory materials therein; in particular in connection with the attachment of labels to rubber-based products such as tires. It is in connection with the attachment of labels to products including stain-creating, migratory materials therein that the staining problem addressed by the present invention is encountered.
In fact, the most preferred label structure disclosed in the '227 patent is a wrap around structure wherein the surface of the label engaging the container is free of adhesive; overlapping ends being secured together by an adhesive. Although non-wrap-around label structures are disclosed as being within the broadest scope of the invention, an expressed concern relating to the use of such a label structure is that an adhesive required to be used to attach the label to the container would be attacked by the solvent in the container and cause the label to become loose or separate from the container.
The present invention solves and/or minimizes the label-staining problem encountered with the use of prior art label structures adhered to products including stain-creating migratory materials therein; without requiring the inclusion of a metallized surface layer and with the versatility of employing coating technology, either on-line or off-line as desired.